Contact chain circuit for the consecutive preparation of idle outlets in telephone systems



April 2, 1957 H. BRETSCHNEIDER 2,787,741

CONTACT CHAIN CIRCUIT FOR THE CONSECUTIVE PREPARATION OF IDLE OUTLETS IN TELEPHONE SYSTEMS Filed Sept. 29, 1955 INVENTOR, HANs BRETSCHN EIDER BY ATTORN Y United States Patent CONTACT CHAIN CIRCUIT FOR CONSECU- TIVE PREPARATION OF IDLE OUTLETS IN TELEPHONE SYSTEMS Hans Brctschneider, Zurich, Switzerland, assignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application September 29, 1953, Serial No. 383,025

Claims priority, application Germany October 1, 1952 2 Claims. (Cl. 317139) The present invention relates to a contact chain circuit for the cyclic preparation of idle outlets in telecommunication systems, particularly in telephone systems.

Chain circuits have already become known in which, as a rule, an outlet may be immediately used again, after having been released. Such arrangements, however, do not provide an equal working rate of the used outlets. For this reason also contact chain circuits have been suggested in which a blocked outlet can only be seized again subsequently to the blocking of another idle outlet. The last-mentioned type of contact chain circuits has become known under the term cyclic chains.

in such arrangements e. g. a preparation relay, energizing the starting relay of a line finder, will be energized after the setting of the line finder which is to be used prior thereto. The last line finder of the row will cause the energization of the preparation relay of the first line finder of this row, since the starting relays are arranged in a closed chain circuit.

In another cyclic chain circuit arrangement wipers and contact laminations of the fina'l selectors, coupled to the line finders, are used as chain members. The chain contacts, which are checked by the relays of the line finders, are bridged via these chain members. The already used final selectors are retained in a particular switching position taking special care of the connecting through of the starting chain. Only after all connecting sets (line finder-final selector) have been used once in turn, will the final selectors be switched back to normal, and thereby the connecting sets will be co-ordinated into the chain circuit again. The present invention likewise relates to a cyclic chain circuit having the advantage according to which the handling of the individual calling conditions is performed each time in turn, one after another, and in which no overlappings take place during the handling performance, as is necessary in certain other types of line finder circuits. The arrangement is made in a way that the chain relay, preparing an outlet in the case of a calling condition, is already energized prior to the calling condition and pre-energizes the next successive chain relay of the chain circuit with a preparing but not energizing current, and that further, after the handling of said calling condition, the first-mentioned chain relay is de-energized and only the pre-energized chain relay of those following in the chain, is energized and pre-energizes on its own behalf the next successive chain relay, and so on.

In the drawing are shown the line finders LFl, LFZ LFX, representing the outlets, which are prepared for seizure respectively by chain relays Vpl, Vp2, Vpx, via contacts vpl", vp2, vpx". These contacts, when operated, connect the line finders to ground via a start contact an which may be operated in any suitable manner, not shown, and when a line finder is so connected, it may be seized for a call. Since it is desired to have the line finders prepared in succession for seizure, it is necessary to have only one of the relays ice Vpl, Vp2, Vpx operated at a time, and when that relay is released, subsequently to the handling of the calling condition, it is necessary to operate the next successive free relay and no other.

Each one of the Vp-relays has two windings, via the winding 1 of which the energization is performed, and via the winding ll there is perr'ormed the electromagnetic pre-energization of the chain relay and its holding. When starting this contact chain circuit, it is a matter of indifference which one of the chain relays Vp is energized first, since in the course of the further seizings the cyclic succession remains. Relays R1, R2 Rx are respectively associated with the line finders LFl, LFZ LFx, and each is adapted to operate when the setting of the associated line finder has been carried out.

The circuit is prepared for operation by the closing of switch SW which connects ground to the armature of relay Vpx controlling contacts vpx. With this switch closed as shown, it will be seen that a current path exists for all the VP relays over winding 1 thereof. It is assumed that all of these relays operate simultaneously, the opening of break contacts vpl, vp2, vpx will disconnect winding I of all of them. However, winding II of vpx has a direct connection to ground over make contact vpx, while the circuits through windings ll of the other relays include the resistors W11, W12, and wi3 and the current is not sufficient to hold these relays and they release. in the released condition, winding 11 of vpl is connected to ground through resistor wz'l, break contact r1, make contact vpx, and make contact vpx. The circuits through windings II of the other relays except vpx are broken at vpl', vpZ', etc.

Relay vpx th-refore remains operated until relay Rx operates, which takes place when contact an is closed. "1 his circuit may be traced from ground, contact an, contact vpx, line finder LFX, winding of RX to negative battery. The opening of contact rx releases relay vpx and the closing of break contact vpx closes the circuits through the number I windings of the other vp relays. However, since vpl is the only one which has been partially magnetized over its winding II, this relay will operate. The contacts vpjl and vpl of the relay Vpl, will be reversed as soon as the relay is energized. These contacts are designed as make-before-break contacts. That is, when the relay is energized, both the make contacts vpl and vpl will close before the break contacts vpl. open. Conversely, when the relay is deenergized, the break contacts vpl will close before either of the make contacts vpi and vpl open.

By means of contact vpi the first chain relay completes a holding circuit for itself via its winding ll, whereby at the same time the energizing circuit for the remaining chain relays is interrupted. By means of the contact vpl, the ground potential, which is applied via the chain of contacts vp, will be connected via contact r2 and resistance WiZ through the winding 11 of the relay Vp2 towards minus at Si. Over the thus established circuit the second relay of the chain VpZ will be pre-energized but not operated.

After handling the calling condition for the first chain relay by the line finder LFl which is associated with said relay, the R1 relay will operate and the contacts r1 and r1 will be switched over. By cutting off the battery with contact r1 the circuit for chain relay Vp1 will be broken. This will cause its contacts vpl and vpl to be reversed, so that the common chain of energizing contacts vpl-x is closed again. Owing to the fact that the chain relay V122 has been pro-energized, it will pull up via the already-mentioned chain and its winding I. This will cause line finder circuit LFZ to be prepared for seizure over vp2" and the reversing of contacts vp2 and 3 vp2' will cause the energizing circuits of all of the remaining Vu-relays to be interrupted, thus being prevented from pulling up.

All further switching procedures are pe formed in the corresponding order of sequence for chain relays VpZ and Vpx, and thereafter for Vpx and Vpl, as described with regard to the relays Vpl and V 22.

I claim:

1. A contact chain circuit for the successive preparation of idle outlets in telecommunication systems comprising a plurality of outlets, a plurality of having their operating windings connected in parallel, there being one relay for controlling each outlet, means for preparing an outlet for seizure when its controlling relay is operated, chain contact means including break contacts of all of said relays arranged in a chain and connected in series with the windings of all said relays for operating any of said relays, said chain being broken when any relay operates, means responsive to the operation of a relay for locking said relay and for simultaneously partially energizing the relay whose breal; contact is next in the chain, and means responsive to the seizing of an outlet for releasing the operated controlling relay for 4 said outlet, whereby said chain contact means is closed again and the relay partially energized is operated.

2. A contact chain circuit, as defined in claim 1, in which each relay has first and second windings, the chain contact means being connected in series with the first windings of all said relays and the means for locking an operated relay including the second winding of said relay and a contact thereof, said circuit further comprising a resistance for each relay, the means for partially energizing the relay whose break contact is next in the chain comprising connection means completed when a. relay is operated for connecting the resistance for the relay whose break Contact is next in the chain between the second Winding of said relay and the locking means of said operated relay.

References Cited in the file of this patent UNITED STATES PATENTS 2,375,413 Guenther May 8, 1945 2,574,904 Bellamy Nov. 13, 1951 2,590,926 Boyer April 1, 1952 2,606,236 Oberrnan Aug. 5, 1952 

